1. Field of the Invention
Many fruit-producing areas are subject to frost or freeze damage to the fruit during the period when the fruit is budding or blossoming. The necessity for a means to prevent such damage to fruit orchards in such areas is, therefore, well-known. There are several ways of protecting the fruit.
Generally, the temperature will be lowest in still air, and there often will be an inversion where cold air is trapped near the ground. Many orchards use wind machines to move the air in this kind of situation. Wind machines tend to be expensive, and there are many orchards where wind machines are not needed because the orchard already has good air drainage. Regardless of air movement, any orchard may still be subject to frost or freeze damage if the temperature gets low enough.
Another method of protection is to surround the fruit with a finely atomized spray of water, and allow the water to freeze on the bud or blossom. The temperature will tend to stay at 32.degree. F. (0.degree. C.) because of the latent heat of fusion of water. Additionally, the more moist the surrounding air is, the less damage will be done because, the higher the moisture content of the air, the less evaporative cooling there will be of the buds and blossoms.
A third way to prevent frost and freezing damage is to provide heat for the orchard. The most common fuels used in orchard heaters are stove oil, furnace oil and liquefied petroleum gas (usually propane). The two basic requirements for orchard heaters are that they should have good fuel efficiency, and they should be of rugged, simple construction. Some orchards require hundreds of heaters to protect against frost and freeze. Considering that many orchard heaters burn 1 gallon of fuel per hour or more, and that the freezing temperatures may persist for several hours, the fuel bill becomes a substantial expense item, particularly if the cold temperatures continue for several nights. While the heaters are kept in place for the frost season, they are moved out of the way after that time, and are kept outdoors, and sometimes are roughly handled. Consequently, orchard heaters must be of strong construction.
It is an object of this invention to provide an orchard heater that will burn fuel at a comparatively low rate, and will burn the fuel completely.
It is a further object of this invention to provide an orchard heater having vaporized water in the hot air exhaust, in addition to that which is created in the fuel combustion process.
It is further object of this invention to provide an orchard heater of strong and simple construction, having no moving parts.
2. Description of the Related Art
Johnson et al. disclose a vaporizing device wherein a liquid is vaporized within a tube, and the vapor is aspirated from the tube by the flow of the products of combustion surrounding the tube, further assisted by air aspirated through a surrounding outer tube.
Both Diggs patents disclose water vaporized from an external pan on top of the heater. Porter et al. disclose an orchard heater having a pulse-jet type combustion chamber with an installed igniter, and an outer casing surrounding the combustion chamber and air inlet pipe.
The patents to Hobby, Olsen, Filliol and Robinson et al. disclose more-or-less standard vertically-oriented orchard heaters.
Higgins discloses a mobile heater with a motor-driven fan.
Barker discloses a salamander-type space heater.